Loss of Control is defined under s54 and s55 of Criminal Justice Act 2009.
s54(1) Criminal Justice Act 2009 gives the elements:
The killing resulted from D's loss of self-control
The loss of self-control had a qualifying trigger
A person of D's sex and age, with a normal degree of tolerance and self-restraint and in the circumstances of D might have reacted in the same or similar way.
The loss of control must be triggered by fear of serious violence of things said or done.
s54(2) It does not matter whether or not the loss of control was sudden.
s54(4) Excludes the defence when it is motivated by a considered desire for revenge.
s55(3) Fear of serious violence.
s55(4) Things said or done or both which caused D to have a justifiable sense of being seriously wronged.
s55(6)c The face that thing done or said constituted sexual infidelity is to be disregarded.
Clinton.
It doesn't matter is the loss of control was sudden or not. This should allow the "slow burn" defence to be used.
Ahluwalia.
s55 defines the "qualifying trigger"
There are two triggers:
Fear of serious violence
Things said or done or both which caused D to have a justifiable sense of being seriously wronged.
Fear of serious violence means that the D fear need to be genuine and if the violence was "serious".
Things said or done must cause the D to have a justifiable sense of being seriously wronged.
Bowyer.
Hatter: Constituted circumstances of an extremely grave character.
A person of D's sex and age with a normal degree of tolerance and self-restraint and in the circumstances of D might have reacted in the same or in a similar way to the D.
The standard of self-control doesn't change but the situation does.